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1、City Viaduct entrance ramp traffic character study autor：LI Yingshua，XU HuiThe rapid development of the automobile industry and the relative lag of the road construction have constituted a prominent contradiction all over the world,particularly, in most of large cities. To cope with it,elevated road
2、s have been built in many cities both at home and abroad. However, traffic jams frequentlyappear on elevated roads immediately after the completion of their construction. The awkward situation mainly results from the planning bug or the unsuitable control, apart from drastic increase in transportati
3、on demand. Elevated roads, ramps and ground roads areclosely interconnected in three-dimensional urban traffic networks.The mathematical modeling and numerical simulation were conducted for the sections of. elevated roads and for the interaction of elevated roadsand intersections on the ground. Afte
4、r having analyzed the complicated dynamic behavior on the elevated roads, some suggestions were put forward for the transportation planning and management. The contents of the dissertation are as follows:(1) By combining manpower survey with the video recording, a series of field measurements were c
5、onducted on several sections of the elevated road system in Shanghai City and then the main characteristics of composed of the Common Language Runtime (CLR) and a unified set of class libraries. ations were established, which are suitable for the free flow and the congested flow respectively. And th
6、us two important parameters, namely, the free flow speed and the jamming density, were determined. The fundamental diagram obtained from the measured data reveals three distinct traffic phases.(2) With the Wuning Of-fRamp of the Inner Ring Elevated road in Shanghai City as a representative case, met
7、iculous observations were carried out on traffic flow at the intersection near the of-framp. And it was found that the squeezing effect of right-turning vehicles from the intersecting main road on the straight motion of vehicles from the of-framp is the main reason of the existing traffic jam. A mod
8、ified 1- D model. With the modified model, numerical simulation was performed with special attention to the disturbing effect of right-turning vehicles. The results agree quite well with the observed data. The analysis shows that the squeezing effect, which exacerbates with the increasing number of
9、right-turning vehicles, is the principal cause of congested traffic at certain intersec tions. The inappropriate design and construction of ramps in front of busy crossings enhances the congestion. Thus, installing the right-turning traffic lights may be a promising way of solving the problem.(3) Th
10、ere exist severe problems in the transportation on elevated road system in Shanghai City, such as frequent congestions or jams on the elevated roads and their ramps. For this reason, measures of controlling the on-ramp traffic with timing signals were suggested in this dissertation. The reasonable t
11、iming scheme was recommended for signal controlling. On the basis of an anisotropic hydrodynamic traffic model developed by our research group, a ramp-effect term was introduced in the motion equation and traffic flows on the elevated road sections near the on-ramp were numerically simulated. The re
12、sults show that signaling control of on-ramp is helpful for the improvement of traffic on the elevated roads. We also found the best timing scheme after comparison among six choices of signaling period.(4) The gear-alternating regulation was first actualized at the interfluent location of on-ramps i
13、n Shanghai elevated roads, which was theoretically studied in this dissertation. Different traffic flow models were established for the cases with and without the alternate running rule based on the FI cellular automaton traffic model. With the models, the traffic behavior at the interfluent locatio
14、n of on-ramp was investigated and some results were concluded. When there are many inflowing vehicles on the elevated road and ramp, the traffic situation on the elevated road with the alternating regulation is much better than that without the regulation; when there are less inflowing vehicles, the
15、 elevated road situation keeps unvaried on the whole in the two cases. The vehicles on the elevated road and the on-ramp are easily to move forward with 1: 1 pro-portion in congestion or free flow states and often with 2: 1 proportion in the medium-speed flow.(5) The weaving areas often turned into
16、the bottleneck on the elevated roads. On the basis of the NS cellular automaton traffic model, the weaving section with one-lane main road was simulated and analyzed.For the free traffic flow, weaving operations almost has no influence on the system, even with the weaving length being increased. On
17、the other hand, when the traffic flow is in congested state, weaving conflicts have negative effects on the system. The traffic situation will be improved with the increase of weaving length. Our simulation results suggest that the length of weaving sections need not to be inappropriately increased,
18、 and a proper medium value can be chosen to get an optimal traffic situation.Finally, the prospect was briefly reviewed for the future advances in the research of urban traffic flows in China.待添加的隐藏文字内容2City expressway on-ramp control are mainly local single ramp Independent control and a handful of
19、 ramp coordination control, the current game.The Department of ramp control most research only for independent ramp control research.Investigate. Many city expressway ramp was very close, a lot of ramp.The distance is only 200 300 m, the ramp in the operation of traffic.Flow interference is very ser
20、ious, in this case on the relative.The entrance ramp for independent control is not reasonable. In this paper Shanghai City Expressway actual testing data, the 2 main near.Distance ( distance of less than 450 m ) entrance ramp traffic flow characteristics in study.Based on bus enter or exit operatio
21、n mechanism，the realistic traffic capacity model of bus stop is established combined with reduced loading areas of bus stop，and then，the standard design mode of bus bay stop is worked out And according to the different road grade of main trunk road，sub trunk road and branch road，model and sizes of b
22、us bay stop set at the intersections and road sections are made integrated designs The design mode has been applied in the Suzhou Industrial Park，which can provide essential reference for urban road design，especially the bus stopTraffic control means is: focus on the elevated road itself from macros
23、copical angle measures, for articulation section microscopic insufficient consideration. Because the present our country real time traffic information collection.Technology needs to be further improved, by means of avoiding Ramp Traffic Control Regional congestion queuing and the validity of the res
24、tricted. In view of the exit ramp.Link Road and traffic flow characteristics, traffic management has taken a different turn through means of organization, including lane function division, ban and other methods, to hold block queuing and the improvement effect was more timely. But in view of differe
25、nt exit ramp connecting sections, how to adopt the different traffic organization,At present there is no systematic theoretical analysis and research. How to make a continuous flow with stop to organic join, make full use of resources, make the system of the optimal, for elevated road and ground roa
26、d system construction and operation a special significance.Ramp presence becomes limiting articulation section inlet tract operation important factor, according to the traffic demand and supply balance principle, should ensure that the exit ramp connecting the highway capacity and the ramp and the g
27、round to flow to match, make traffic can timely discharge, system is maintained in a relatively stable state. To ban the articulation section, traffic operation mode and the general intersection similarity, this does not do the special analysisTraffic control measures that is by setting the signal l
28、amp, the conflict points distribution of traffic flow in different time periods, so as to achieve at the same elevation pavement to eliminate conflict point; stereo cross measure that is by setting the engineering facilities, the conflicting traffic arrangement in different elevation on the road, in
29、 order to achieve various time range to eliminate the conflict point; roundabout measures that is by setting the large center island, interwoven into the ring road and vehicle running around the island, will intersect the traffic stream is converted to interlaced stream, at various time within the s
30、ame elevation on the road to eliminate the conflict points, far leading circuitous measures its practice is actually the conflict is converted to interlaced, disappear in addition to conflict point.City Road in intersection traffic flow, has been generally take the measures to eliminate, reduce conf
31、lict point. According to interweave, confluent, diverting traffic impact on the relatively few studies and countermeasures. If the city road traffic volume is not within the time period or region, interweave, shunt, the effect of relatively in acceptable condition, study its impact on traffic and Co
32、untermeasure of urgency is not obvious, but as the city increase of traffic, especially the city expressway construction, it is necessary to interweave shunt, confluence, the implications for further study, and research to improve the flow of traffic improvement measures. Based on the characteristic
33、s of city road network, its characteristic is generally more developed road network, the relatively small spacing, a lot of old urban road network distance between 200 to about 600 m, mixed traffic flow on road network traffic capacity influence is increasingly serious, with the city expressway cons
34、truction, elevated expressway in the city built the use of existing road width layout, avoid a large number of residents, this mode of construction in large city, typical example is the Shanghai inner ring viaduct. With the elevated expressway construction, to contact the rapid transit and ground sl
35、ow traffic, according to the traffic needs to set up the ramp traffic conversion, but according to now run the examples, more traffic problems in the ramp and ground traffic conversion between. In view of the above problems, the article on the city road network space is smaller under the conditions
36、of mixed flow of traffic capacity and the effect of improving measure to undertake preliminary discuss on network distance, the larger is the special study.With the development of City Road, city road builders gradually realize that: in the city road network conditions, especially because of various
37、 historical reasons, the planning of road network conditions and causes of expressway construction demand there is a gap between. But the city expressway construction is the city development, transportation development one of the important means to solve, it is necessary to research the road builder
38、s in various adverse conditions, improving the traffic capacity of the road, in the limited hardware construction conditions to provide greater traffic capacity. On the light control, grade separation construction, various research and engineering example, the crossover controlled and improved not o
39、nly devoted to exploring, concern the improvement of city expressway ramp with surface intersections between matching problem, undertake preliminary discuss, the generalized point, this article referred to the improvement measures not only can be applied to the expressway and the ground city crossing engineering, various influences larger sections, intersections can refer to.